1. Field of the Invention
The present invention relates to a method for preparing anhydrous metal salts. More particularly, the invention relates to a method of preparing anhydrous metal salts by using a crystalline aluminosilicate material as a means for absorbing and removing the water of hydration from a hydrated metal salt.
2. Description of the Prior Art
Anhydrous metal salts are conventionally prepared by a variety of techniques. United States Pat. No. 3,799,746 shows a method of forming anhydrous aluminum chloride in which chlorine gas is passed by means of graphite lances into molten aluminum at a temperature of 1300.degree. C to 1500.degree. C. The vaporous, anhydrous aluminum trichloride which is produced by the process is passed via a conduit to a condenser upon which the anhydrous aluminum trichloride condenses.
Various procedures are known for preparing anhydrous magnesium salts which also are involved and complicated procedures. Thus, U.S. Pat. No. 3,440,006 shows a method of preparing anhydrous magnesium halide which is substantially free of magnesium oxide by admixing a saturated solution of a hydrated magnesium halide in absolute alcohol with a cycloaliphatic ether. A metal halide complex forms which contains both alcohol and ether molecules and which is insoluble in the alcohol solvent. After separation, the complex is heated, whereby the organic solvents in the complex are liberated thereby forming a magnesium halide product substantially free of magnesium oxide. United States Pat. No. 3,975,283 discloses a technique of preparing magnesium chloride by adding a gelling agent to a brine solution containing magnesium chloride. The gel is spray dried to prepare the anhydrous magnesium halide product. A relatively complex procedure of preparing anhydrous magnesium chloride is disclosed by U.S. Pat. No. 3,983,224 in which a slurry of MgCl.sub.2 is formed in the diethyl ether of tetraethylene glycol and an azeotropic agent which has a boiling point less than the ether. Distillation of the slurry results in the removal of water from the halide salt. However, several other steps are necessary before the desired anhydrous magnesium chloride can be eventually obtained. U.S. Pat. No. 3,341,282 reveals a method of dehydrating carnallite (KCl.MgCl.sub.2.6H.sub.2 O) to eventually yield anhydrous magnesium chloride. In the process, the ore is roasted at temperatures of preferably about 600.degree. F to remove the water of hydration. The residue is then treated with an alcohol, preferably a C.sub.3 to C.sub.8 alcohol and is heated to effect solution of the magnesium chloride salt over the alkali metal halide impurities. The alcoholic solution containing dissolved magnesium chloride is then treated with ammonia, thereby forming a complex magnesium salt ammonia precipitate. The precipitate is then heated to remove ammonia and liberate traces of the alcoholic solvent. It is evident from the above discussion that the prior art procedures for preparing anhydrous salts are complicated and most often involve the use of high temperatures and occassionally corrosive atmospheres.
A need, therefore, continues to exist for a simple and effective method of preparing anhydrous metal salts which does not require the use of high temperatures and ocrrosive materials.